This math topic involves calculating areas of portions of rectangles. It specifically focuses on identifying the area of shaded or specified portions, based on the total area of the rectangle and the fraction of it that is shaded or marked. The problems provided require multiplying the full area by a given fraction (like 1/2 or 3/4) to determine the area of the part of the rectangle that is filled in. This theme falls under a broader category of learning about area and perimeter logic.